tableadapter update problem

Question

I can't seem to update the datasource when I call the tableadapter's update method.  Here is my code snippet:

DealsTableAdapter ta = new DealsTableAdapter();
dsDeals.DealsDataTable dt = new dsDeals.DealsDataTable();
dsDeals.DealsRow dr = dt.NewDealsRow();
dr.NominalRate =varNewRate;
ta.Update(dr);

The update command on the table adapter looks like this:

UPDATE    Deals
SET  NominalRate = @NominalRate

If I use the query builder, and supply a parameter value for NominalRate, it works.  But otherwise, no.

I am not sure what I am missing here.  Can anyone help?

Andy